Mammography has long been used to screen for breast cancer and other abnormalities and for diagnostics. Traditionally, mammograms were formed on X-ray film, but more recently flat panel digital imagers have been introduced that acquire a mammogram in digital form and thereby facilitate analysis and storage and provide other benefits as well. Further, X-ray tomosynthesis of the breast has been proposed recently, as discussed in the earlier-filed applications identified above, and clinical testing has been carried out. The assignee of this patent specification, Hologic, Inc., has demonstrated at trade shows in this country a fused, multimode mammography/tomosynthesis system that takes either or both types of images, and either while the breast remains immobilized or in different compressions of the breast. Dedicated breast tomosynthesis systems also have been proposed.
Tomosynthesis as used in the systems and methods disclosed in this patent specification typically involves acquiring a plurality of tomosynthesis projection images Tp at respective angles relative to the breast, and reconstructing therefrom a plurality of tomosynthesis reconstructed images Tr representative of breast slices that have selective thicknesses. Proper display techniques are desirable to make the presentation of Tp and/or Tr images (collectively referred to here as T images) more effective and efficient for review by health professionals. When tomosynthesis projection images Tp are acquired along with conventional 2D mammograms Mp, improved display methods are desirable that facilitate the display of both T and Mp images. Effective display approaches also are desirable when tomosynthesis images Tp and/or Tr that are acquired at one time need to be compared to mammograms Mp and/or to tomosynthesis images Tp and/or Tr acquired at a different time. Effective displays also are desirable when only Tr and/or Tp images are being displayed. Another display issue relates to Computer Aided Detection (CAD) methods that use computer analysis of images to identify locations and possibly other characteristics of suspected abnormalities. CAD marks currently are placed on or are otherwise associated with mammogram images Mp, but it may be useful to place them at the appropriate location on Tr and/or Tp images o to otherwise associate them with Tr/Tp images. Conversely, it may be desirable to obtain CAD marks by processing Tp and/or Tr images, and place them at appropriate locations on Mp images. Here the notation Mp refers to a conventional mammogram, which is a two-dimensional projection image of a breast; the term Mp encompasses both a digital image as acquired by a flat panel detector or another imaging device and the image after conventional processing to prepare it for display to a health professional or for storage, e.g. in the PACS system of a hospital or another institution. Tp refers to an image that is similarly two-dimensional but is taken at a respective tomosynthesis angle between the breast and the origin of the imaging X-rays (typically the focal spot of an X-ray tube), and also encompasses the image as acquired as well as the image after being processed for display or for some other use. Tr refers to an image that is reconstructed from images Tp, for example in the manner described in said earlier-filed patent applications, and represents a slice of the breast as it would appear in a projection X-ray image of that slice at any desired angle, not only at an angle used for Tp or Mp images. The terms Tp, Tr and Mp also encompasses information, in whatever form, that is sufficient to describe such an image for display, further processing, or storage. The images Mp, Tp and Tr typically are in digital form before being displayed, and are defined by information identifying properties of each pixel in a two-dimensional array of pixels. The pixel values typically relate to respective measured or estimated or computed responses to X-rays of corresponding volumes in the breast (voxels or columns of tissue).
Yet another issue concerns the large storage requirements of tomosynthesis images Tp and/or Tr. Because the reconstructed datasets for Tr images are large, it may be better in some circumstances to store unreconstructed projections images Tp, which require less storage. Transmission times to the storage device, and from the storage device to the display workstation, can thus be reduced. The Tp images in this case can be reconstructed to Tr images just prior to viewing that requires a display of Tr images. Further, it may be desirable that images viewed on a workstation are the same or at least comparable to images viewed on a different workstation, or the same or at least comparable to previously viewed images of the same dataset, even if the software and/or hardware of the workstation or acquisition system or intermediate storage or processing systems, have changed.
Yet another issue concerns the processing time required to reconstruct tomosynthesis images Tr. Because of relatively long reconstruction times, one possible approach is to perform reconstructions at an acquisition console, and send the already-reconstructed images to display workstations. This can allow a greater reading throughput if there are several acquisition systems that are all pushing images to one or more display workstations. The system can be designed so that it can handle M acquisition consoles sending their images to all N display workstations.
In one non-limiting example disclosed in this patent specification, acquisition and display of x-ray images starts with acquiring x-ray mammography image data representative of projection mammography images Mp of patients' breasts and x-ray tomosynthesis image data representative of projection images Tp taken at different angles of at least a source of imaging x-rays relative to the patients' breasts (e.g., different angles of the focal spot in an X-ray tube relative an immobilized breast). This acquisition can be performed by a single unit, using a single X-ray tube and a single flat panel digital imager or some other imaging device, configured to selectively acquire one or both of the mammography and tomosynthesis image data, in the same compression of a patient's breast or in different compressions, and at the same imaging session or at different times. The disclosed system and method use at least a subset of the acquired Tp images to form reconstructed tomosynthesis images Tr representative of slices of the breasts that have selected orientations and thicknesses. The system and method display at least a selected subcombination of the Mp, Tr and Tp images, preferably for concurrent viewing or at least for viewing in a single session, and preferably but not necessarily while showing, at or near the displayed images, respective labeling symbols identifying them as Mp, Tr or rp images and possible other information that facilitates detection/diagnosis of abnormalities, such as information indicative of the position and orientation of the slices represented by Tr images, the thicknesses of such slices, etc. The information can be in alphanumeric or non-numeric form such as in the form of graphics and/or icons.
The method and system can further generate or otherwise obtain computer aided detection (CAD) marks for suspected abnormalities in said Mp images, and can display said marks at corresponding locations on or in association with Tr and/or Tp images that are related, e.g. by orientation or otherwise, with respective Mp images. In addition to location information, the CAD marks can provide information regarding, for example, the type of suspected abnormality and/or a confidence level that a mark points to an actual abnormality. CAD marks that are initially generated from or are otherwise related to some of the Tr, Tp or Mp images can be displayed at or in association with images from which they were not generated or with which they were not initially associated, at corresponding or at least related locations. Tp images can be stored together with version information indicative of at least one of an acquisition configuration used to acquire them and a reconstruction configuration used to reconstruct Tr images from said Tp images, to thereby enable later reconstruction of Tr images that match those reconstructed at an earlier time. Alternatively, or in addition, Tp images can be stored together with version information related to when they were acquired and can be later reconstructed into Tr images using a reconstruction configuration that matches the version information. A reconstruction configuration can be provided that has at least two different versions of reconstruction software, so that Tr images can be reconstructed using a version of the reconstruction software that matches the version information of the Tp images or earlier Tr images. Tr images can be reconstructed from only a subset of the acquired Tp images, which in an extreme case means reconstruction from a single Tp image to yield a Tr image that is equivalent of the Tp image. Tr images representative of at least two breast slices that differ in thickness can be formed, for example using MIP (Maximum Intensity Projection) methods or a summing method that may or may not use different weighting of the summed pixel data. The display can be toggled between Tr images representative of breast slices having different thicknesses, wherein the slices may or may not overlap in space. Through computer-processing, the volume of a lesion can be computed and displayed from information contained in the Mp, Tr and/or Tp images. The display can show concurrently, for example, Tr images reconstructed from a current acquisition of Tp images and at least one Mp image obtained from a previous acquisition involving a different breast compression. The concurrent display can be on the same or different display monitors, and can include at least Mp and/or Tr images, or at least Mp and/or Tp, images, or at least Tr and/or Tp images, or all three types of images, and can instead or additionally include 3D images formed from some or all of the acquired X-ray data, image data and/or from Mp, Tr and/or Tp images. Information indicative of status of loading Tr images for display can be shown as a part of the display. Different images can be displayed at different pixel sizes or fields of view or, alternatively, they can be selectively equalized by pixel size or field of view by selected types of interpolation or extrapolation, for example by up-converting to a smaller pixel size and thus a higher converted pixel count or by down-converting to a larger pixel size and thus a lower pixel count.
The display of Mp and T images such as Tr images can include displaying non-numeric indications of various properties of the displayed images. Such non-numeric indications can include indications of respective levels, spacing and slice thickness for displayed Tr images relative to a compressed breast imaged in an Mp image or relative to some other frame of reference, for example in the form of cross-lines on a bar related to the breast as displayed as an Mp image, wherein the height of the bar may relate to the thickness of the compressed breast, and/or non-numeric indications of respective thicknesses of breast slices represented by displayed Tr images, for example in the form of cross-bars of respective thickness on a bar related to Mp images, and/or non-numeric indications of the inclination angle of the slice or slices represented by one or more Tr images relative to a selected frame of reference such as the compressed breast that was imaged to generate the data from which the Tr images were reconstructed, and/or non-numeric indications of other parameters. Instead, or in addition to such non-numeric indications, numerical indications can be provided and displayed of the position of a slice image Tr relative to, e.g., a breast imaged in an image Mp, the thickness of the slice represented in a Tr image, and/or the orientation of that slice. Mp and T images such as Tr images can be shown overlaid on each other, and toggling can be allowed to switch between the image that is visible at the time and an image that is not, i.e. toggling between the 2D Mp image and the 3D Tr image or images. Similar toggling is available between different types of T images, of between different T images of the same type. In addition, other image display effects can be provided, such as, without limitation, fade-in/fade-out and blending two or more images at respective weightings, image overlays and masking, or other effects, as commonly used in post-production of television images and in known image processing software such as Photoshop from Adobe.
T images such as Tr and/or Tp images can be displayed in cine mode, with selective control over the speed of changing from one image to another, the order of images for display relative to an order in which they were reconstructed or acquired, the selection of the first and last images in the cine sequence, and/or other parameters. For example, at least two sets of Tr images, each set reconstructed from different acquisitions of Tp images, can be shown concurrently and scrolled through and/or displayed in cine mode in synchronism. For example, the two sets of Tr images can be synchronized such that the first and last slice images of each set can appear on the display at the same time, which may be implemented in different ways, such as by making the number of images the same (but possibly representing slices of one thickness in one set and slices of a different thickness in the other set), or by scrolling through images of one set faster than through images of the other set, or in some other way. Making the number of Tr images of one set match that of the other set may involve interpolating images of new slices to either reduce the number of images/slices in one set or increase it. The images in that case in one set of Tr images can be made to represent slices that are all the same thickness or slices that include some that are thicker or thinner than other slices.
Tr images can be displayed in scroll or cine mode in different orders, such as by starting with the image representing the bottom of the breast (the breast side resting on a breast platform during imaging) toward to image representing the top of the breast (the breast side compressed by a compression paddle), or in reverse order, or by starting with a Tr image representing a selected intermediate slice and proceeding toward the top or the bottom of the breast, or in some other desired order. The initial image that is displayed can be the bottom image, the top image, or a selected intermediate image. In a scroll or cine mode, the display can show every image of a Tr set for a breast, or a selected subset, such as every other image or some other subset of all Tr images representing a breast. The display system can have a default mode for a new user in which it starts the scroll or cine display with the bottom image, but with provisions for this default to be changed to another display protocol for that user in which the starting image is another one of the Tr images. A selection of initial or default display modes can be provided relating to the order, speed, slice thickness and/or other parameters of display of images, and user selection among those modes can be allowed. Similar procedures are available in the case when the orientation of the Tr slices is not the same as that of the Mp or Tp slices.
Thus, information regarding image data acquisition, storage, reconstruction and/or other parameters can be selectively displayed. For example, Tr images can be identified on the display as such, thus providing an image type indication display, and additional identification can be displayed in association with a displayed image that identifies the position in the breast of the slice represented by the displayed Tr image, the thickness of the slice, the orientation of the slice, and/or some other property associated with the displayed Tr image. Corresponding or at least similar display of information can be associated with different types of displayed images, such as Tp and Mp images and displayed in association with the display of the images. In the alternative, images such as Tr, Tp, and/or Mp can be displayed in different combinations and/or sub-combinations that may include the same type of images displayed concurrently or toggled, or different types of images displayed concurrently or toggled, without providing some or any of the identifications discussed above. Tr images can be printed in an N×M format (where N and M are positive integers), and printing of any images displayed on one or more monitors in WISIWIG format can be provided.
Compression of Mp, Tp, and/or Tr images and/or of other image data can be selectively carried out prior to storing or archiving the images. The compression can be lossless, or it can be lossy to a selected degree. Reconstruction of Tr images can be selectively carried out from compressed Tp images, preferable after suitable decompression. Window/level controls can be provided for at least selected ones of the displayed Tr images, and the controls can be set by the user, or automatically, to control the window width and/or the window level of only one, or only selected ones, or all of the displayed images. Image regions can be magnified for display, and the window/level controls automatically applied to the magnified regions. The Tr, or the Tp, or both the Tr and Tp images, can be stored in PACS storage, and can be associated with related Mp images and/or with selected CAD information. The Tp images can be acquired by using coarser binning, e.g. in a direction of relative motion between the source of imaging x-rays and a breast during image acquisition, or in both directions. Alternatively, such binning can be done after the Tp images are acquired, to thereby reduce storage and further processing requirements. The Mp, Tr, and/or Tp images that are concurrently displayed can be based on image data acquired from the same breast of a patient while the breast remains immobilized under compression that can remain the same or change between the acquisition of Mp images and Tp images. Alternatively, the Mp and Tp images can come from different acquisitions at different times or different breast compressions. Image data for Tp images acquired at two or more acquisition units can be supplied to and reconstructed into Tr images at a single reconstruction unit, from which one or more data display units can acquire Tr, Tp, and/or Mp images for display, or image data for Tp images can be stored as such and only reconstructed into Tr images immediately prior to display thereof. Images with difference characteristics such as pixel size, brightness, gamma curves, etc. can be processed to make selected ones of their characteristics sufficiently similar to facilitate comparison.
An additional or alternative display approach uses the Tp and/or Tr images in stereoscopic display. For example, when any two Tp images taken at different angles to the breast are displayed concurrently and viewed such that each is seen by a different eye of the observer, depth information is visualized. Similarly, when any two Tr images are reconstructed such that their image planes are at an angle to each other, depth information can also be perceived.
Images of different types and from different sources can be displayed in desirable size and resolution. For example, an image can be displayed in (1) Fit To View Port mode, in which the size of the displayed image size is maximized such that the entire imaged breast tissue is visible, (2) True Size mode, in which a display pixel on the screen corresponds to a pixel of the image, or (3) Right Size mode, in which the size of a displayed image is adjusted so that it matches that of another image that is concurrently displayed or with which the displayed image is or can be toggled. For example, if two images of the same breast are taken and are not the same size or do not have the same special resolution, provisions are made to selectively zoom in or zoom out one of them, or zoom both, such that they appear to be the same size on the screen when they are concurrently displayed or the user toggles between them, to facilitate comparison or to otherwise facilitate detection/diagnosis. Known interpolation/extrapolation and weighting techniques can be used in such re-sizing, and known image processing technology can be used to make other characteristics of the displayed images similar in a way that facilitates detection/diagnosis.
Selected hanging protocols are provided that are unique to the different types of images with which the disclosed system deals. As one example, the hanging protocols for 2D images (e.g. Mp images) and 3D images (e.g. Tr images) are linked so that when one type of image is displayed for a given breast the other type is displayed as well. For example, when the Mp image of a breast is displayed, a tile of the Tr images and/or of the rp images is automatically displayed at the same time, with a desired hanging protocol that may involve scrolling or cine mode presentation, or may require user input so select a particular subset of the Tr and/or Tp images or a particular individual Tr/Tp image. Thus, a combined hanging protocol set can be provided for 2D and 3D images that are concurrently displayed or toggled such that only one type is displayed at one time. In addition, the combined hanging protocol can include provisions for linked display of CAD information associated with one or both of the 2D and 3D images involved in the hanging protocol. Alternatively, the hanging protocols for 2D images are made different from those for 3D images.
When CAD information is available that is associated with any of the images that can be displayed, linking can be provided such that CAD information derived from one of the types of displayed images can be automatically associated with corresponding locations on another displayed image. For example, if CAD information has been derived on the basis of an Mp image and the Mp image is displayed at the same time as, or is toggled with, Tr images, provisions are made to selectively display CAD information associated with the appropriate locations on Tr images. Alternatively, if CAD information is derived on the basis of Tr and/or Tp images, it can be automatically selectively displayed in association with an Mp image that is displayed at the same time or is toggled with the Tr/Tp images. In one example, an Mp image with CAD marks thereon remain displayed on the screen while Tr images of the same breast are scrolled or shown in cine mode on the screen, to facilitate identification and/or assessment of suspected abnormalities in the Tr images.
When Tr images are displayed, provisions are made to selectively adjust the thickness of the slice represented by any displayed Tr image. For example, if it is desired to display a Tr image of a slice (slab) of breast tissue that is 1 cm thick but the available Tr images represent 1 mm thick slices, 10 of those Tr images can be combined into a single new Tr image that represents the 1 cm slice, using for example a known MIP (maximum intensity projection) technique.
For storage, transmission to remote locations, and/or other purposes, the images can be formatted consistent with DICOM standards. For example, each raw or displayed projection image set or reconstructed slice image set for a single view is stored as a single Secondary Capture image instance according to DICOM. The image pixel data can be encoded in a selected compressed format (CODEC) that includes all projection or slice images